Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Taxes [Line Items]
Interest expense carryovers	$ 6,457
Operating loss carryforwards, valuation allowance	21,100	$ 2,900
Unrecognized tax benefits if unrecognized, the balance of uncertain tax benefits would impact the effective tax rate	$ 4,900	4,900	$ 4,900
Domestic Tax Authority [Member]
Income Taxes [Line Items]
Net operating loss carryforwards not subject to expiration		$ 194,200
Effective income tax rate reconciliation, at federal statutory income tax rate, percent	80.00%
Interest expense carryovers	$ 29,100
Domestic Tax Authority [Member] | 2027-2038 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	562,600
State and Local Jurisdiction [Member] | 2022-2042 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 233,500
Minimum [Member] | Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2027
Minimum [Member] | State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2023
Maximum [Member] | Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2038
Maximum [Member] | State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2043